Absorbent bodies of absorbent articles such as disposable diapers and sanitary articles generally employ superabsorbent polymers (hereunder also referred to as “SAP”) and pulp.
The commonly used SAP materials at the current time include synthetic polymer-based SAP such as polyacrylate-based polymers, but in recent years much attention has become focused on naturally derived SAP such as polyglutamate-based polymers, from the viewpoint of biodegradability.
For example, International Publication No. WO 2007/034795 A1 discloses a method for obtaining a biodegradable polyglutamate gel with excellent swelling and moisture retention properties, at a high yield, using a water-soluble carbodiimide and an N-hydroxysuccinic acid imide as a condensation agent and condensation adjuvant during crosslinking of poly(glutamic acid) with a polyamine.
In addition, Japanese Unexamined Patent Publication No. 2009-114391 discloses, for increased SAP gel liquid flow speed and water absorption under load, an absorbent including a water-soluble vinyl polymer and/or a hydrolyzable vinyl monomer, as well as a crosslinked polymer having a crosslinking agent as an essential structural unit, and smectite.